Physioex Exercise 2 Lab and Review Sheet Activity 2

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Exercise 2: Skeletal Muscle Physiology:
Activity 2: The Effect of Stimulus Voltage on Skeletal Muscle Contraction Lab Report Pre-lab Quiz 1. Skeletal muscle fibers are innervated (stimulated) by c. motor neurons.
2. A single action potential propagating down a motor axon results in d. a single action potential and a single contractile event in the muscle fibers it innervates. 3. In resting skeletal muscle, calcium is stored in

c. the sarcoplasmic reticulum.
4. During the latent period for an isometric contraction
c. the cellular events involved in excitation-contraction coupling occur.

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Experiment Results Predict Question:
Predict Question:
As the stimulus voltage is increased from 1.0 volt up to 10 volts, what will happen to the amount of active force generated with each stimulus? c. The active force will first increase and then plateau at some maximal value as the stimulus voltage increases. Stop & Think Questions:

What do you see in the active force display when the stimulus voltage is set to 0.0, and why does this observation make sense? a. 0.00 g; there was no activation of skeletal muscle fibers by this stimulus. What is the lowest stimulus voltage that induces active force in the skeletal muscle? b. threshold voltage 6.

Review Sheet Results
1. Describe the effect of increasing stimulus voltage on isolated skeletal muscle. Specifically, what happened to the muscle force generated with stronger electrical stimulations and why did this change occur? How well did the results compare with your prediction? As the stimulus increased the muscle tension also increased but not in proportion. The threshold voltage was 0.8 and it yielded a significant increase in muscle tension but as the stimuli continued the muscle force increased in smaller and smaller amounts until it reached a plateau when all the motor units available were activated. 2. How is this change in whole-muscle force achieved in vivo? Whole muscle force...
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